Field of the Invention
This invention relates to door hardware and, more specifically, to a surface/cremone bolt for locking a door.
Description of the Prior Art
Surface bolts have long been used for locking a door with respect to the surrounding frame and wall. Generally, the surface bolt comprises multiple keepers having an arcuate cross section and mount to the door to define a channel in which a surface bolt is slidable. The keeper channel defines a longitudinal axis along which the surface bolt moves. The surface bolt has a knob for actuating the surface bolt and the interior of the surface bolt defines a channel in which a guide is received. The guide sets within a recess in the keeper and has an extension which is disposed within the channel of the surface bolt. The extension defines an aperture in which a spring and a ball bearing are disposed. The spring forces the ball bearing to contact the surface of the inner wall of the surface bolt.
Typically, a mortise strike plate is mounted to the door jamb adjacent the door and in alignment with the surface bolt so that by sliding the surface bolt with the handle, the surface bolt will extend into the mortise strike on the wall and lock the door with respect to the wall. Previous surface bolts are susceptible to binding because the clearance between the keeper, surface bolt and guide is great enough that the surface bolt can veer away from the longitudinal axis and bind with respect to the keepers and the surface bolt. Thus, it is desirable to make a surface bolt that is self-centering to avoid the binding during movement of the surface bolt.
A cremone bolt is similar to a surface bolt but has two bolts connected by a handle that activates both bolts on rotation or movement of the handle. One bolt extends upwardly from an upper portion of a door and the other bolt extends downwardly from a lower portion of a door into a strike plate in a door jamb. The construction of the cremone bolt assembly is similar to the surface bolt assembly discussed above, especially with respect to the bolt and guides.